Study: Jellyfish and eels don’t push water to move forward

University of South Florida’s research team has revealed that jellyfish doesn’t move forward in water by creating a wave-like body motion to push against the water, instead it sucks the water toward them.

Dr. Brad Gemmell, assistant professor in the Department of Integrative Biology, University of South Florida, along with a team of scientists from five institutions, studied the movement of these marine animals and found an astonishing fact that could change the way we think about jellyfish’s movement in the water.

Earlier, many researchers have proved that jellyfish and eels can move from point A to point B without spending more energy. These marine animals use very less energy than any other animals, birds or creatures (runner, flier, swimmer, etc.). Till now, the secret behind the energy efficiency was a mystery.

Dr. Brad Gemmell stated:

“Until now, it has been widely assumed in the literature and the textbooks that animals swim primarily by pushing against the fluid to generate high pressure and move the animal forward. However, it turns out that at least with some of the most energy efficient swimmers, low pressure dominates and allows these animals to pull themselves forward with suction.”According to scientists, animals move is directly related to the ecological impact, fitness and evolutions. This study will be helping the engineers who study bio-inspired design to invent efficient underwater vehicles by taking ideas from nature.

Scientists have also experimented on lamprey, an eel-like underwater animal to understand the secret behind the movement with undulating, wave-like body motions. The team has observed these animals by putting them in a tank of water with smaller glass beads, and then illuminating them with a laser. These glass beads placed in such a way as to enable visualization of the flow and timing to better understand the animals’ movement. They have recorded these movements using high speed cameras in fractions of a second to study the ‘hydrodynamic efficiency’ of the process.

According to the study, jellyfish and eel-like creatures create a pocket of low-pressure water inside each bend of their body to move forward in the water using undulating motions. When these animals create low-pressure water, the water ahead of these animals rushes into the low-pressure zone, hence, pushing the animal forward. That means, jellyfish and lampreys don’t push the water for their movement, instead they force the water to push them forward by creating low-pressure pockets, hence, reducing their energy spendings.

The research has been published in the journal Nature Communications, on November 3.